46 PLIOCENE MOLLUSCA. 



be abundant, we are indebted to Mr. Jas. Keeve, from whose collection in the 

 Norwich Castle Museum the specimen here figured is taken ; it has been found 

 since by Mr. W. M. Crowfoot at Beccles. Messrs. Kennard and B. B. Woodward 

 report it from West Runton, but state it has not been detected in any Pliocene 

 deposit on the Continent of Europe ; they consider it cannot be distinguished from 

 P. suilla, Dybowski, of Lake Baikal. 



In their paper on the non-marine mollusca of the alluvium of the river Lea,^ 

 written in 1904, they remarked that "among nine species of Pisidium, the most 

 noteworthy is P. supinum, hitherto undetected in these islands. The specimens 

 were large, but not so fine as those found in the Pleistocene of Grays." They are 

 of opinion that eventually it will be found to have been widely distributed in 

 Pleistocene and Holocene times. 



Pisidium Henslowanum (Sheppard). Plate I, fig. 22. 



1825. Tellina Henslowana (Leach, MS.), Sheppard, Trans. Linn. Soc, vol. xiv, p. 150. 



1881. Cyclas appendieulata, Turton, Man. Land Freshw. Shells, p. 15, fig. 6. 



1833. Pisidium Henslowianum, Jenyns, Trans. Camb. Phil. Soc, vol. iv, p. 308, pi. xxi, figs. 6 — 9. 



1840. Pisidium Henslowianum, G-ray, Man. Land Freshw. Shells., p. 285, pi. i, fig. 6. 



1844. Pisidium Henslowianum, Brown, 111. Conch. 6t. Brit., ed. 2, p. 95, pi. xxxix, fig. 25. 



1852. Pera appendieulata, Leach, Moll. Brit. Syn., p. 292. 



1853. Pisidium, Henslowianum, Forbes and Hauley, Brit. Moll., vol. ii, p. 131, pi. xxxvii, fig. 11. 

 1862. Pisidium fontinale, var. Henslowana, Jeffreys, Brit. Conch., vol. i, p. 21. 



1875. Pisidium (Fossarina) Hensloivanum, Saiidberger, Land Sussw. Conch. Vorw., p. 763, pi. xxxiii, 



fig. 3. 

 1913. Pisidium Henslovjamim, B. B. Woodward, Cat. Brit. Sp. Pisidium, p. 93, }A. ii, fig. 4 ; pi. iii, 



fig. 9; pi. xxiii, figs. 21 — 31 ; pi. xxiv ; pi. xxv, fig. LS ; pi. xxvi, fig. 13. 



Specific Characters. — Shell small, thin, rather tumid, oblique, sub-ovate, very 

 inequilateral, finely but irregularly striated concentrically ; ventral margin rounded, 

 dorsal straight and sloping ; posterior side blunt, rounded below, subangulate 

 above ; anterior elongate, compressed ; umbones prominent, acute, furnished with 

 a small laminar projection which in the adult occupies the summit of the shell, 

 appearing like a ridge rising up vertically on either side of the hinge ; hinge strong; 

 anterior laterals nearly half the length of the latter. 



Dimensions. — L. 5 mm. B. 4 mm. 



Distribution. — Recent : most widely diffused in Central England; very rare and 

 local in Wales, Ireland and Scotland ; on the continent from Siberia to Sicily. 



Fossil: Coralline Crag : Sutton. Freshwater bed : West Eunton. 

 Widely diffused in the English Pleistocene, as at Grays, Ilford, Lea valley, Edmonton, 

 Stutton, Clacton, Barnwell, Woodston, Cropthorne ; found also at many places in 

 the British Holocene deposits. 



Pleistocene of Europe from Sweden to the south of Prance (Jeffreys). 



1 Essex Nat., vol. xiii, p. 20, fig. 3, 1904. 



